This invention relates to apparatus for selectively transferring data between display registers and, more particularly, to such apparatus which finds particular use in video editing apparatus wherein data representing the relative position of a video record medium may be transferred, as desired, from one display register to another so as to establish and control an edit operation.
In the general field of data recording, it often is desirable to create a finalized recording derived from portions of pre-existing recordings and other sources of data. It also is desirable to modify one recording by selectively inserting thereinto various bits and pieces which are derived from other recordings. Such creations and modifications of recordings are referred to generally herein as "editing".
While editing is used generally in most fields of data recording, it has become a highly specialized and advantageous technique in the field of video recording. Thus, video signals which are recorded on a particular record medium, such as a magnetic tape, a magnetic disk, or the like, are "edited" by selectively assembling or inserting other video signals onto that record medium. For the purpose of the present discussion, the record medium on which the video signals are recorded is described as magnetic tape which, presently, is the most common form of record medium that now is used for recording video programs. Typically, in the field of broadcast and commercial video tape recording, video signals which are recorded on one tape are reproduced by a video tape recorder (VTR) for an "insert" or "assemble" recording by another VTR on recording tape. As is known to those of ordinary skill in the art of video editing apparatus, an "insert" edit operation describes the insertion of video signals into a predetermined location on a video tape, the "inserted" signals being preceded and followed by pre-existing video signals. In an "assemble" mode of operation, video signals are recorded in following relation (i.e. assembled) to pre-existing information.
As is recognized, to carry out the insert and assemble edit modes of operation, it is necessary for an operator to select appropriate portions, or blocks, of video signals which are to be reproduced from one tape (referred to generally as the source or playback tape) and which are to be recorded at other locations on the recording (or destination) tape. That is, the operator must be aware of the particular addresses on the source tape at which desired video signals are recorded as well as addresses on the destination tape at which new video signals are to be placed. These "addresses" on the respective video tapes generally are recorded as time code addresses, each of which separately identifies a respective frame of the recorded video signal. An example of one type of time code address which is used with, for example, the recording of NTSC signals is the so-called SMPTE (Society of Motion Picture and Television Engineers) time code which represents frame addresses in terms of hours, minutes, seconds and frames up to a maximum value of 23 hours, 59 minutes, 59 seconds and 29 frames. Although other acceptable time code addresses are known, for convenience, and in the interest of simplification, the present discussion refers only to this SMPTE time code.
It is conventional to record the time code longitudinally, that is, in serial tracks along a length of the video tape. Time code generators and readers are known for the recording and reading of such time codes as the video tape is transported. These time codes, as read from the video tape, are used to designate so-called "edit-in" and "edit-out" locations of the respective playback and recording tapes.
To carry out an edit operation, the time code addresses which identify the particular frames on the playback tape which define the video information that is to be re-recorded on the recording tape are marked, or stored, as the edit-in and edit-out points. For an insert edit mode, the desired edit-in and edit-out points on the recording tape likewise are marked, or stored. Of course, for favorable results, that portion of the playback tape which subsists between the edit-in and edit-out points should be equal to the corresponding portion on the recording tape. Once the operator confirms that the material, or video signals, lying between the edit-in and edit-out points on the playback tape is correct and should be re-recorded between the edit-in and edit-out points on the recording tape, the actual transfer of video signals may occur. Such confirmation of this edit operation is known as a "preview", and the previewed operation may be monitored on a suitable video display monitor device. If changes are to be effected to the respective edit-in and edit-out points, for example, if the operator finds other material which he wishes to transfer from the playback tape to the recording tape, or material which should be deleted from the recording tape, the time code addresses which define the respective edit points may be suitably changed.
In an assemble edit mode of operation, it may not be necessary to define an edit-out point for the recording tape. This is because, in the assemble edit mode, the selected video signals which are reproduced from the playback tape, and which lie between the edit-in and edit-out points thereon, merely are added to (i.e. assembled) the previously-recorded video signals on the recording tape commencing from the edit-in point thereon.
In many types of VTR edit apparatus presently available, respective edit-in and edit-out points for the playback and recording tapes can be stored merely by operating suitable selector switches when the respective tapes arrive at their desired time code addressed locations. However, the edit-in and edit-out points for each tape often are not displayed. This makes it difficult for the operator to effect relatively small, or fine, adjustments to these respective points. Also, the operator is deprived of important information which, advantageously, would assist him in carrying out an edit operation.
Another disadvantage of VTR edit apparatus which presently is available is the difficulty in transferring time code addresses for effecting modifications in the various edit points that have been selected. For example, let it be assumed that the operator has selected one particular edit-in point for the playback tape. Upon reviewing this tape, he may determine that, possibly, another edit-in point should be selected. In the aforementoned presently available VTR edit apparatus, only one of these edit-in points can be selected and stored. Consequently, the operator must undertake a rather laborious and time-consuming task to compare the two edit-in points which he has selected in order to determine which of these points ultimately should be used. There is, therefore, a need to store two or more time code addresses from which the operator easily can choose which one is to be used in the actual edit operation. In conjunction with this need is a need to permit easy transfer of such stored time code addresses, preferably by simple push-button operation.
Another disadvantage of presently available VTR edit apparatus is the difficulty in effecting simple modifications to the edit-in and edit-out points. For example, there is no or limited ability to increase or decrease selected edit-in and edit-out points by desired amounts.
A still further disadvantage in many presently available VTR edit devices is that, once a particular edit point has been changed, the previous edit point cannot be recalled. For example, if an edit-in point is changed from one time code address to another, the preceding address generally is not retained, thus making it difficult for the operator to compare the results of his newly selected edit-in point with the previously selected edit-in point. This may complicate the manipulations which are needed in order to determine a proper edit-in point at which the actual edit operation is carried out.